


The Secret Nobody Knows

by SmallBirds



Category: Supernatural
Genre: M/M, Smut, Wincestiel - Freeform
Language: English
Status: Completed
Published: 2015-06-17
Updated: 2015-06-17
Packaged: 2018-04-04 19:06:28
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,048
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/4149429
Author URL: https://archiveofourown.org/users/SmallBirds/pseuds/SmallBirds
Summary: <blockquote class="userstuff">
              <p>Sam isn't surprised by Dean and Cas' developing relationship. What DOES surprise him is his own curiosity. </p><p>//Adapted from a tumblr fic I wrote a while back.</p>
            </blockquote>





	The Secret Nobody Knows

Sam isn’t an idiot.

He knows almost immediately when Cas and Dean’s relationship becomes more than platonic. He couldn’t quite put his finger on what gave them away; a softening of their expressions, perhaps, or Dean brewing two cups of coffee in the morning instead of one, the coffee maker giving it’s final gurgle as Cas walks barefoot into the kitchen, sleep in his eyes.

Sam notices the way their fingers linger as they brush up against one another when they do the dishes (Dean washes, Cas dries, Sam puts away). To be honest, he isn’t all that surprised. There have been several occasions over the years when, in his opinion, the sexual tension between his brother and the angel could have been cut with a knife.

And he's seen the way Dean stares at Cas when he putters around the bunker, barefoot and soft in his borrowed clothes, muttering to himself over some arcane text. He watches his brother watch the fallen angel, and recognizes that Dean for all the world looks like a drowning man spotting dry land.

So no, Sam isn’t surprised by their developing relationship. And the first two times he catches them, it’s completely by accident.

 

The initial time, it’s a simple matter of Dean leaving his goddamn door open. Sam wakes up thirsty in the middle of the night, and casually glances into his brother’s room as he passes by on his way to the kitchen.

It takes his sleep-addled brain a full five seconds to comprehend that Cas has his brother bent in half in front of him and is fucking into him so hard that the headboard is shaking and Dean’s moans are being muffled into a pillow. Sam squeaks and slaps his palms to his eyes, running blindly back to his room and spending the rest of the night with a pillow over his head, trying to ignore the muffled _harders_ and _fucks_ and _Cas_ coming from the room down the hall.

The next morning he blushes his way through breakfast, burning his toast and fumbling with the butter knife until Cas places a cool hand on his forehead and asks him if he feels alright. He stands close enough that Sam can smell his ridiculous lavender shampoo and see down the collar of his shirt to the vividly purple hickey sucked onto the delicate ridge of his collar bone.

Sam gives up on breakfast and retreats to his room to lie down for several hours.

 

The second time they don’t even have the decency to be caught under the cover of darkness. He’s in the stacks of the library, searching for a particularly rare tome of 16th century spells when he hears soft voices and peeks his head around the shelf.

Dean and Cas have entered the library while he was in the stacks, and while their initial intention may have been research, Dean now has his jeans down around his ankles and is fucking himself in and out of Cas’s mouth with every sign of approval from the angel kneeling at his feet.

Cas’s approach is messy and enthusiastic, licking sloppily up his shaft before taking him all at once. Dean groans out a curse when Cas swallows him up to the hilt before sucking his way up slowly, pulling off him with an audible pop. He has his hand curled in Cas’s hair, and he uses it to lift the angel up to his feet. Dean crashes their mouths together while Cas replaces his mouth with his hand, jacking the older Winchester with a tight fist.

“Come for me,” Cas growls, his voice like sandpaper on velvet, and Dean does so with a moan that starts in his mouth and ends in up Cas’s, convulsing in the angel’s arms and making a mess of his shirt.

Sam sits with his back to the stacks, face burning, and desperately attempts to ignore the sudden tightness of his jeans. He stays prone for a full twenty minutes after his brother and the angel leave before bolting to the bathroom and taking an ultimately unhelpful cold shower.

When he wakes up that night, it’s from feverish dreams of broad backs and spit-slicked skin, and he has to wash his sheets.

 

The third time he catches them, he’s just come home from a hunt. He’d been tracking a lone vamp wreaking havoc through Kentucky for the better part of two weeks, and he’s exhausted and filthy, and he’s pretty sure he smells like seven kinds of gross.

He calls ahead to let them know he’s on his way home and not to wait up for him, but that he’d love them forever if there were clean towels waiting for him when he arrived. Dean is quiet for a moment on the other end of the line, then says “Of course, idiot, what are we, amateurs?” and disconnects the call. Too tired to be annoyed, Sam tosses his cell in his duffel bag and starts the long drive home.

The bunker is quiet when he pulls into the garage in the dark hours of the morning. He toes his boots off in the living room and walks on silent feet up the stairs to his bedroom, wincing at the ache in his muscles ( _fucking vampires_ ) and thinking warm thoughts about his bed.

There are two fluffy towels waiting for him in his room, and he sighs gratefully as he strips off his dirty clothes, tossing them in the direction of his hamper before walking down the hall to the bathroom.

The shower is everything he could have hoped for, hot water sluicing down his back and washing away a week’s worth of blood and grime. In his head he drafts a long and arduous love letter to the bunker’s water pressure, waxing more and more lyrical as the hot water pummels into his aching muscles. After scrubbing his body nearly raw, he reluctantly shuts the water off and steps into the foggy bathroom. He wraps a towel around himself and pads down the hall towards his room, pausing when he hears what sounds like a sob coming from behind Cas’ bedroom door.

With a denseness he later attributes to exhaustion, and with the memory of the awful nightmares Cas had suffered from after his first week as a human still fresh in his mind, Sam doesn’t think twice about opening the door to check in on the former angel.

Cas is on all fours, back arched and hands wound tight in the sheets. His skin is tawny and gilded in the soft light of his bedside lamp, and he trembles as he undulates under Dean’s hands. The elder Winchester is kneeling behind the angel on the bed, running one hand along Cas’s spine as he fucks three fingers into him from behind, leaning over to leave bite marks on his shoulder blades, all the while whispering to him, _yes, fuck, Cas, so pretty, so tight_.

Cas’s head snaps up and suddenly he and Sam are staring at each other. Sam simultaneously realizes he’s been standing in the doorway staring for the better part of thirty seconds and _Oh, God_ , he’s painfully, obviously aroused, tenting the towel around his waist.

The younger Winchester stumbles back, shame and arousal burning his face red, and is about to run for the hills when Cas moans “Sam?” in a wrecked, rough little voice that burns it’s way through Sam’s body, and reaches out for him.

Sam freezes, eyes wide on Cas's as his instincts scream for him to run. Dean does something with his fingers and Cas trembles. This time when he beckons, his hand shakes. Sam takes an automatic step forward, glancing at his brother and feeling his pulse jump at the dark delight on Dean’s face. He pauses in the center of the room, unsure of his role in this tableau, until Cas glares at him and huffs “Get the hell over here,” and Dean grins and chuckles, “You heard the man, Sammy,” and Sam thinks, _Oh, crap_ , and closes the distance between their bodies.

Everything is hot and rough and electric, buzzing with the slide of his skin on theirs as they pull apart and crash back together. Cas licks into his mouth, burning and intense, hands clutching at his jaw possessively. He tastes the way static electricity feels, and a shudder trips up Sam’s spine as he moves between them, his brother ( _his brother, oh_ fuck) and his angel. Dean bites down on his shoulder, making him gasp, and then flattens his tongue over the abused area.

“You wanna fuck him, Sammy?” He purrs, sliding a calloused palm up the inside of Sam’s thigh. Sam whimpers, and Cas’s eyes go dark, pupils dilating with want as he guides Sam’s big hand between his legs. “Feel me, Sam,” he whispers shakily. “Dean got me all ready for you.” Sam hears himself hiss out a curse as he watches first two, then three of his fingers disappear into the tight heat of Cas’ hole.

Dean slides his hand up and slowly fists his brother’s cock, smearing his shaft with the precome leaking from his swollen head and pulling another strangled whimper out of him. Cas jerks, and he moans into the hollow of Sam’s neck, hands scrabbling at his biceps. “Please,” he hisses, and Sam is barely aware of moving before he has Cas on his back, ass up, thighs pressed to his chest.

His eyes are electric, beautiful in his flushed face and focusing so intensely on Sam that he throbs with it. For a split second he wonders how his brother can stand it, feeling that naked under another person’s gaze all the time, like having his soul held under a magnifying glass and inspected for cracks. Then Dean is guiding him into Cas, and Sam can’t think of anything but the heat and the tightness and the way Cas rolls up to meet him, gasping words that are sometimes in English and sometimes not. He hears his name in there, and Dean’s, and, strangely, hearing his brother’s name on the angel’s lips as he fucks into him makes the heat coiling in his abdomen tighten even more.

Dean is everywhere, leaving a burning trail of kisses down Sam’s chest and fisting Cas’s cock and his own in time with Sam’s thrusts, murmuring sweet praises in between shudders and gasps ( _so good, so hot, Sammy you’re fucking him so good_ ) until Sam snaps and yanks him forward, crashing their mouths together in a filthy kiss, all savage tongue and nipping teeth. Beneath them, Cas comes with a strangled shout, cock pulsing hot and wet onto his lean stomach.

Sam can’t last much longer with all that clenching heat around him, and he makes a desperate grab for Dean’s hand and then he’s slamming into Cas again and again as the heat builds and builds and builds and then Dean says “C’mon, Sammy,” his voice wrecked, and Sam is coming, harder than he ever has, vision spotting, collapsing onto his brother’s shoulder and trying to remember how to breathe. Distantly he hears Dean’s choked _fuck_ , and then he feels wetness paint his side and he knows that Dean has come apart beside him.

He feels hands stroking his hair and running down his chest, and slowly, slowly he pulls out, groaning through his oversensitivity and the angel’s wet heat. Cas beams up at him, satisfied and happy, and pulls Sam down to curl against his body.

He feels Dean settle in behind him, spooning around his back and tangling their legs together, the way he used to when they were kids and Sam had nightmares. Sam buries his face in the hollow of Cas’s clavicle and smiles.

“We should clean up,” he mutters drowsily, and Cas presses a kiss to his forehead.

“Later,” he says, gently, but Sam is already asleep. He isn’t awake to see Dean’s grin, or to hear him say “I told you that would work,” in smug, hushed tones, or to see Cas’s answering eye roll as he swats his lover on the arm.

He sleeps, pressed between the two people he loves most in the world, and for the first time in years he does not dream.


End file.
